An H or an O isn't enough for a hydrogen bond
- The idea
- Predict
- See it
- Why
- Check
The idea
“Any molecule with oxygen or hydrogen atoms can form hydrogen bonds.”
The name makes it sound like any hydrogen will do. What counts is what the hydrogen is attached to.
The short version
The mistake: Any molecule with oxygen or hydrogen atoms can form hydrogen bonds.
What's actually true: A hydrogen bond needs an H bonded to O or N, drawn to a nearby O or N. Hydrogens on carbon can't form one.
- Oxygen and nitrogen are electronegative. They pull shared electrons away from a bonded H, leaving it partly positive.
- That H is drawn to a partly negative O or N nearby. That pull is a hydrogen bond.
- Carbon and hydrogen share electrons almost evenly, so an H on carbon stays nearly neutral.
On the exam: H on O or N can hydrogen bond. H on C can't.